Re: Better way to code an iterator function?

[Mark Feldman <mfeldman@...>]

Are you trying to avoid backtracking the index or keeping its previous 
value? How about this:

function it_paths(paths)
   local function next(state, var)
       local result
       result, state.idx = paths[state.idx], state.idx+1
       return result
   end
   local state = {idx = 1 };
   return next, state, "";
end;

Mark Feldman

Lawrence E. Bakst wrote:
> 1. Is there a better, shorter, cuter, or cooler way to code the example below?
>
> 2. I guess something I didn't try was to "deep copy" paths, use that as the state, and then remove one element at a time from the state.
>
> 3. This is probably FAQ, but I couldn't find much with a quick search on Google.
>
> I miss C's pre/post inc/dec operators and I can't be the only one. Is there any way to make inc and dec functions that increment or decrement the number passed in and return the previous value? Seems difficult in a language that only has pass by value for numbers and strings.
>
> Thanks in advance for all help and suggestions.
>
> function it_paths(paths)
>     local function next(state, var)
>         if (state.idx > #paths) then return nil end;
>         state.idx = state.idx + 1;
>         return paths[state.idx - 1];
>     end
>     local state = {idx = 1};
>     return next, state, "";
> end;
>
> function process_random_files(paths)
>     for path in it_paths(paths) do
>         print(path);
>     end
> end
>
> process_random_files{"foo", "bar", "baz", "quuz"};
>
>   


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